1. Field of the Invention
The present invention relates generally to the fields of guidance and control actuators. More particularly, it concerns swash plate guidance and control actuators that may be used to guide and control spinning objects including missiles and projectiles.
2. Description of Related Art
Various means have been used to guide spinning objects such as non-spin stabilized missiles while in-flight toward their intended targets. A common means for accomplishing in flight guidance in the past has been to include adjustable fins, vanes or wing planes on the projectile. In the past, pneumatic and hydraulic control mechanisms or several electric motors were used to control each pair of wing planes. The problem with the aforementioned devices has been that generally one pneumatic or hydraulic cylinder or electric motor was required for each wing. The problem with the prior art control devices was that because of the plurality of prime movers required, they were complicated, expensive to manufacture, and frequently used an excessive amount of allocated space.
Additional problems and complications arise when trying to guide and control spin-stabilized objects. For high-spin-rate objects, one typically attempts to affect control by means of fins or the like. To make a lift maneuver in one direction for such objects, one must typically apply a sinusoidal lift direction into the fins at the spin rate of the object in order to induce a lift in one direction. This requires, in turn, that the bandwidth of the actuators be some multiple of the spin rate of the object. In fact, if multiple motions need to be applied to a spinning fin, it may be necessary to implement a control loop having a speed several times faster than the spin rate of the projectile.
Due to the high rate of objects such as missiles and rounds, the need to keep up with, and control, spinning fins necessitates very high bandwidth and often complicated actuators. Such actuators may be quite expensive and consume a lot of powerxe2x80x94two factors that inhibit the ability to produce low-cost rounds. In fact, due to limited bandwidth, the maximum spin rate of a missile or round may be established, and indeed limited, by the point at which the actuator can no longer effectively control the missile.
In an attempt to address such limitations, others have designed products to de-spin objects to some reasonable rate that may be controlled by existing actuators. In fact, some have chosen to de-spin objects all the way down to a zero spin rate so that effective fin control may be more easily achieved. Although these approaches have exhibited some degree of utility, de-spinning an object is not always desirable. In particular, the de-spinning necessary to achieve control often sacrifices stability that could be provided by a higher, albeit uncontrollable spin rate. Further, de-spinning wastes critical time, which may limit the ability to steer to close-in targets.
In light of at least the above, methodology allowing for the control and guidance of highly spinning objects (such as missiles, rounds, munitions, projectiles, etc.) that is not unduly limited by actuator bandwidth would be advantageous. Particularly, methodology that reduces, or eliminates the need to de-spin an object in order to affect control would be most desirable.
In one respect, the invention is an apparatus for controlling an object spinning at a first rate in a first direction. The apparatus includes a swash plate, a rotor, a spin actuator, a roll actuator, and a pitch actuator. The rotor is coupled to the swash plate. The spin actuator is coupled to the rotor and is configured to spin the rotor in a second direction opposite the first direction. The roll actuator is coupled to the rotor and is configured to displace the swash plate along a longitudinal axis. The pitch actuator is coupled to the rotor and is configured to tilt the swash plate in a tilt direction about the longitudinal axis.
In other respects, the spin actuator may be configured to spin the rotor at a second rate substantially equal the first rate. The apparatus may also include one or more control rods coupled to the swash plate, the control rods being configured to couple to one or more guidance members of the object. The spin actuator may be configured to spin the rotor in the second direction at a third rate not equal to the second rate to adjust the tilt direction. The spin actuator may include a spin motor, a spin pinion coupled to the motor, a spin gear coupled to the pinion, and a spline drive coupled to the gear and to the rotor. The roll actuator may include a roll motor, a roll pinion coupled to the motor, a roll gear coupled to the pinion, and a roll drive screw coupled to the gear and to the rotor. The pitch actuator may include a pitch motor, a pitch pinion, a pitch gear coupled to the pinion, and a pitch bearing coupled to the gear and to the rotor. The pitch actuator may be coupled to a roll drive screw. The object may be a missile.
In another respect, the invention is an apparatus for controlling an object spinning at a first rate in a first direction, including a swash plate, a rotor, a spin actuator, a roll actuator, and a pitch actuator. The rotor is coupled to the swash plate. The spin actuator is coupled to the rotor and is configured to spin the rotor in a second direction opposite the first direction at a second rate. The roll actuator is coupled to the rotor and is configured to displace the swash plate along a longitudinal axis. The pitch actuator is coupled to the rotor and is configured to tilt the swash plate in a tilt direction about the longitudinal axis, the tilt direction being adjustable by adjusting the second rate relative to the first rate. The roll actuator is coupled to the pitch actuator so that the pitch actuator keeps a substantially identical orientation with the swash plate as the swash plate is displaced along the longitudinal axis by the roll actuator.
In other respects, the second rate may be substantially equal the first rate. The apparatus may also include one or more control rods coupled to the swash plate, the control rods being configured to couple to one or more guidance members of the object. The spin actuator may include a spin motor, a spin pinion coupled to the motor, a spin gear coupled to the pinion, and a spline drive coupled to the gear and to the rotor. The roll actuator may include a roll motor, a roll pinion coupled to the motor, a roll gear coupled to the pinion, and a roll drive screw coupled to the gear and to the rotor. The pitch actuator may include a pitch motor, a pitch pinion, a pitch gear coupled to the pinion, and a pitch bearing coupled to the gear and to the rotor. The roll actuator and the pitch actuator may be coupled to a roll drive screw. The object may be a missile.
In another respect, the invention is a method for controlling an object spinning at a first rate in a first direction. One or more guidance members of the object are coupled to a swash plate. A rotor coupled to the swash plate is spun in a second direction opposite the first direction at a second rate substantially equal the first rate. The swash plate is tilted about a longitudinal axis with a pitch actuator coupled to the rotor to affect a change in pitch of the object.
In other respects, the coupling may include coupling one or more fins to one or more control rods coupled to the swash plate. The method may also include displacing the swash plate along a longitudinal axis with a roll actuator to affect a change in the first rate. The displacing of the swash plate does not, in one embodiment, substantially affect the orientation of the pitch actuator with the swash plate. The object may be a missile.
In another respect, the invention is a method for controlling an object spinning at a first rate in a first direction. One or more guidance members of the object are coupled to a swash plate. A rotor coupled to the swash plate is spun in a second direction opposite the first direction at a second rate. The swash plate is tilted in a first tilt direction about a longitudinal axis with a pitch actuator coupled to the rotor to affect a first change in pitch of the object. The rotor is spun in the second direction at a third rate to adjust the first tilt direction to a second tilt direction about the longitudinal axis. The swash plate is tilted in the second tilt direction with the pitch actuator to affect a second change in pitch of the object.
In other respects, the coupling may include coupling one or more fins to one or more control rods coupled to the swash plate. The method may also include displacing the swash plate along a longitudinal axis with a roll actuator to affect a change in the first rate. The displacing of the swash plate does not, in one embodiment, substantially affect the orientation of the pitch actuator with the swash plate. The object may be a missile.